Error in Converting a Map to ConcurrentMap in Java [duplicate]

Question

I have a Map<String,Object> to be converted to a ConcurrentMap<String,Object>

    Map<String,Object> testMap = new HashMap<String,Object>();
    testMap.put("test", null); //This null causing issues in conversion
    testMap.put("test2","123");
    testMap.put("test3",234);
    ConcurrentMap<String,Object> concMap = new ConcurrentHashMap<>(testMap);

I get a null pointer exception. If I copy to a new HashMap<String,Object>

    Map<String,Object> testMap = new HashMap<String,Object>();
    testMap.put("test", null);
    testMap.put("test2","123");
    testMap.put("test3",234);
    Map<String,Object> concMap = new HashMap<>(testMap);

I don't get any errors. Is there a safe way to a Map<String,Object> to a ConcurrentMap<String,Object> without the NullPointerException

Answer 1

If you look into the source code of ConcurrentHashMap you will see, it doesn't allow null key or value -

java.util.concurrent.ConcurrentHashMap#putVal

/** Implementation for put and putIfAbsent */
final V putVal(K key, V value, boolean onlyIfAbsent) {
    if (key == null || value == null) throw new NullPointerException();

Answer 2

It's in the documentation for ConcurrentHashMap:

Like Hashtable but unlike HashMap, this class does not allow null to be used as a key or value.

As for other ConcurrentMaps, the only other implementation ConcurrentSkipListMap, does not allow null either.